On the Accretion Origin of a Vast Extended Stellar Disk around the Andromeda Galaxy

  title={On the Accretion Origin of a Vast Extended Stellar Disk around the Andromeda Galaxy},
  author={Rodrigo A. Ibata and Scott C. Chapman and Annette M. N. Ferguson and Geraint F. Lewis and Michael Irwin and Nial Tanvir},
  journal={The Astrophysical Journal},
  pages={287 - 313}
We present the discovery of an inhomogenous, low surface brightness, extended disklike structure around the Andromeda galaxy (M31) based on a large kinematic survey of more than 2800 stars with the Keck DEIMOS multiobject spectrograph. The stellar structure spans radii from 15 kpc out to ~40 kpc, with detections out to R ~ 70 kpc. The constituent stars have velocities close to the expected velocity of circular orbits in the plane of the M31 disk and typically have a velocity dispersion of ~30… 

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